Six Sigma Measurement Yield and Defects Probability of

Six Sigma Measurement

Yield and Defects Probability of Yield Probability of Defects LSL Target Value USL

The Normal Curve s -6 s -5 s -4 s -3 s -2 s m s s +1 +2 -1 68, 26 % 95, 46 % 99, 73 % 99, 9937 % 99, 999943 % 99, 9999998 % s +3 s s s +4 +5 +6 s 2 s 3 s 4 s 5 s 6 s

Statistical Interpretation of Six Sigma Let “X” be the quality characteristic of interest and (Length/Thickness/Temperature/Pressure etc. ) USL = Upper Specification Limit LSL = Lower Specification Limit T = Target Value m = Process Average s = Process Standard Deviation X = Estimate of m s = Estimate of s

Calculation of Sigma level - When Process is Centered SIGMA LEVEL (Z) = USL - T s OR SIGMA LEVEL (Z) = T - LSL s L Mean = T U

Calculation of Sigma level When Process is Centered Closer To LSL SIGMA LEVEL (Z) = L Mean T X - LSL s U

Calculation of Sigma level When Process is Centered Closer To USL SIGMA LEVEL (Z) = L T USL - X s Mean U

Calculation of Sigma level There is only Upper Specification Limit (USL) SIGMA LEVEL (Z) = Mean USL - X s U

Calculation of Sigma level There is only Lower Specification Limit (LSL) SIGMA LEVEL (Z) = L X - LSL s Mean

The Normal Curve wit Different Sigma Levels S = 2 (SIX SIGMA Quality Level) S = 3 (FOUR SIGMA Quality Level) S = 4 (THREE SIGMA Quality Level) 1298 = LSL USL = 1310 USL = 1322

SIGMA (s) QUALITY LEVELS (DPMO) SIGMA LEVEL DPMO 1 2 3 4 5 6 6, 97, 700 3, 08, 537 66, 807 6, 201 233 3. 4

Converting Yield to Sigma Level Without Shift

Opportunities for Defect DPMO ¨MEANS DEFECTS PER MILLION OPPORTUNITIES ¨IS TRANSLATED INTO A SIGMA NUMBER

Defects/Opportunity & Defect/Million Opportunity Formula = Number of Defects # of Units x # of opportunities Example 319 Defects, 1150 Items, 15 defect opportunity 319 defects on joints Formula = 1150 Units x 15 opportunities/joist = 0. 018 DPO = 0. 018 x 106 = 18, 000 DPMO